Flow cytometry and T-cell response monitoring after smallpox vaccination

Evaluation of Cross-Immunity to the Mpox Virus Due to Historic Smallpox Vaccination

When the Mpox virus (MPXV) began spreading globally in 2022, it became critical to evaluate whether residual immunity from smallpox vaccination provided cross-protection. To assess the cross-immune response to MPXV, we collected serum samples (n = 97) and PBMCs (n = 30) from healthy-donors, either born before 1974 and reporting smallpox vaccination during childhood or born after 1975 and not vaccinated with Vaccinia virus (VACV)-based vaccines. We evaluated the levels of anti-MPXV IgG and neutralizing antibodies (Nabs) and the presence of a T cell response against MPXV. We found anti-MPXV IgG and Nabs in 60 (89.6%) and 40 (70.1%) vaccinated individuals, respectively. We observed a T cell response to Orthopoxviruses and MPXV peptide pools in 30% of vaccinated individuals. We thus show that a high proportion of subjects who received the smallpox vaccine 40 to 60 years ago have humoral cross-immunity, while the T-cell-specific response against MPXV was observed in a smaller group (30%) of vaccinated individuals. This study, combined with information on immunity developed during natural infection or the administration of current vaccines, will contribute to a better understanding of humoral and cellular responses against MPXV.

Anti-Pneumococcal Vaccine-Induced Cellular Immune Responses in Post-Traumatic Splenectomized Individuals

PURPOSE

Splenectomy is associated with increased risk of overwhelming post-splenectomy infections despite proper anti-pneumococcal vaccination. As most studies concentrated on vaccination-induced humoral immunity, the cellular immune responses triggered in splenectomized patients are not yet well studied. The present study aims to investigate this area as it can contribute to the development of more effective vaccination strategies.

METHODS

Five healthy and 14 splenectomized patients were vaccinated with pneumococcal conjugate polysaccharide vaccine (PCV) followed by pneumococcal polysaccharide vaccine according to the guidelines established by Advisory Committee on Immunization Practices. PBMC samples collected 0, 8, and 12 weeks after PCV immunization were in vitro stimulated with PCV. Levels of lymphoproliferation, T_H cell differentiation, and cytokine release were assessed by carboxyfluorescein succinimidyl ester labeling, intracellular cytokine staining, and ELISA, respectively.

RESULTS

While T_H1-dominated immune response was detected in both groups, asplenic individuals generated significantly lower levels of T_H1 cells following in vitro stimulation. Similarly, levels of IFN-γ, IL-4, and IL-17 release and lymphoproliferation were significantly lower in asplenic patients.

CONCLUSIONS

According to our data, splenectomy negatively influences the levels of PCV-induced lymphoproliferation, T_H1 differentiation, and cytokine release. Besides, PCV failed to induce T_H17-dominant immune response which is crucial for protection against extracellular pathogens.

Detailed kinetics of immune responses to a new cell culture-derived smallpox vaccine in vaccinia-naïve adults

The aim of the present study was to investigate the kinetics of humoral and cell-mediated immune responses to a new cell culture-derived smallpox vaccine (CJ-50300, CJ Corporation, South Korea) in 18 vaccinia-naïve volunteers. All subjects achieved positive humoral immune responses (plaque reduction neutralizing antibody assay) 28 days after vaccination, and cell-mediated immune responses (ELISPOT assay) 14 days after vaccination. Humoral immune responses increased up to 28 days after vaccination and were maintained up to 56 days after vaccination. In contrast, cell-mediated immune responses increased up to 14 days after vaccination and steadily decreased to 56 days after vaccination [Clinical Trial No. NCT 00336635].

T-Cell response profiling to biological threat agents including the SARS coronavirus

The emergence of pathogens such as SARS and the increased threat of bioterrorism has stimulated the development of novel diagnostic assays for differential diagnosis. Rather than focusing on the detection of an individual pathogen component, we have developed a T cell profiling system to monitor responses to the pathogens in an array format. Using a matrix of antigens specific for different pathogens, a specific T cell profile was generated for each individual by monitoring the intracellular production of interferon-gamma by flow cytometry. This assay allows for the testing of multiple proteins or peptides at a single time and provides a quantitative and phenotypic assessment of CD4(+) and CD8(+) responding cells. We present profiling examples for several positive individuals, including those vaccinated with the smallpox and anthrax vaccines. We also show antigen optimization for the SARS-hCoV, as studies revealed that these proteins contain peptides which cross-react with more common coronaviruses, a cause of the common cold. The T cell array is an early and sensitive multiplex measure of active infection, exposure to a pathogen, or effective, recent vaccination.

Rapid, differential diagnosis of orthopox- and herpesviruses based upon real-time PCR product melting temperature and restriction enzyme analysis of amplicons

Orthopoxviruses tend to have non-specific early symptoms that cannot be differentiated readily from other infectious exanthemas, such as varicella-zoster virus (VZV) or disseminated herpes simplex virus (HSV) infections. A rapid assay was developed for the differential diagnosis of orthopoxviruses and herpesviruses based upon the melting temperatures of real-time PCR amplicons. A mean melting temperature difference of 8.7 degrees C was observed between the products amplified from the two virus families. Further identification of individual pathogens was made using restriction enzyme analysis. The assay was able to identify correctly viruses from quality control panels of herpes and orthopoxviruses.

The Future of Smallpox Vaccination: is MVA the key?

Eradication of the smallpox virus through extensive global vaccination efforts has resulted in one of the most important breakthroughs in medical history, saving countless lives from the severe morbidity and mortality that is associated with this disease. Although smallpox is now extinct in nature, laboratory stocks of this virus still remain and the subject of smallpox vaccination has gained renewed attention due to the potential risk that smallpox may be used as a biological weapon by terrorists or rogue states. Despite having the longest history of any modern vaccine, there is still much to be learned about smallpox vaccination and the correlates of protection remain to be formally defined. This Commentary will discuss the strengths and weaknesses of traditional smallpox vaccination in comparison with immunization using modified vaccinia virus Ankura (MVA), a non-replicating virus with a strong safety record but weakened immunogenicity.

Immunological memory to viral infection

Immunological memory is defined by the ability of a host to remember a past encounter with a specific pathogen and to respond to it in an effective manner upon re-exposure. How long immunological memory can be maintained in the absence of re-infection continues to be a subject of great controversy. Recent studies on immunity following smallpox vaccination demonstrate that T-cell memory declines steadily with a half-life of 8-15 years, whereas antiviral antibody responses are maintained for up to 75 years without appreciable decline. By combining recent advances in quantitative immunology with historical accounts of protection against smallpox dating back to the time of Edward Jenner, we are gaining a better understanding of the duration and magnitude of immunological memory and how it relates to protective immunity.